1. Field of the Invention
The invention relates to electrical connectors, and in particular to electrical connectors of the type used to couple data communications cables with circuitry on a network or communications interface card.
2. Description of Related Art
The demand for cables and connectors capable of transferring data between computers and peripherals has increased exponentially in recent years as the advantages of networked systems of personal computers, and access to the so-called information highway, have become increasingly evident to users. Despite the increasing popularity of modem communications and networked computer systems, however, and the corresponding tendency towards standardization of system components, there currently exists a wide variety of different cable and connector types, with none likely to attain exclusivity in the foreseeable future. The different cable types currently in widespread use include twisted pair cables and coaxial cables for serial communications, and numerous different multiple wire configurations for parallel communications.
In general, twisted pair cables are coupled to a network or data communications interface via connectors of the type popularly referred to as modular phone jack connectors because of their resemblance to the standard four wire telephone jack connector. This type of connector is commonly denoted by the letters RJ, followed by a numerical indicator (e.g., the RJ 45 connector often used in Ethernet applications). An example of a state-of-the-art modular jack connector with advanced filtering capabilities is found in copending U.S. patent application Ser. No. 08/043,544.
Coaxial cable connections are usually accomplished by a type of connector known as the BNC connector. An example of a state-of-the-art BNC connector with advanced filtering capabilities is shown in copending U.S. patent application Ser. No. 08/075,876.
Multiple wire cables, on the other hand, utilize a variety of different multiple pin connectors, including mini-DIN connectors and D-sub connectors such as the RS-232 standard 25 pin (DB25) connector, or the 15 pin (DB15) connector commonly used in Ethernet cards. Depending on the specific needs of the user, these connectors may be either shielded or unshielded, and may or may not include filter components such as capacitors.
Although each different cable type requires a different connector, the use of separate interface cards for each type of cable or connector is unnecessarily redundant, and thus it is common to provide more than one type of connector on a single card in order to enable the card to communicate with compatible devices which differ only in the choice of cable or connector required. The Ethernet network interface, for example, can interchangeably use all three of the above-mentioned types of cable and thus, in order to provide compatibility with a maximum number of external devices, it is common to provide as many as three different types of connectors on a single Ethernet interface or adapter card.
Fortunately for interface card manufacturers, the three most common types of connectors-modular jack connectors, BNC connectors, and D-sub parallel connectors-are small enough to fit side-by-side on a standard network card. Conventionally, this is accomplished without modifying the connectors. However, it turns out, for reasons which were not previously appreciated by those skilled in the art, that placement of the three standard connectors on a card without modification is a less than optimal configuration.
The first reason why it is disadvantageous to place multiple connectors on a single card without modification of the connectors has to do with the cost of the circuit board on which the connectors are placed. This cost, previously ignored by connector designers, is significant. Even though the space occupied by multiple connectors placed side-by-side on an interface card may be acceptable from the standpoint of compatibility with available slots in the device within which the card is to be used, this space necessitates a larger board than might otherwise be required. Even small decreases in the total footprint of the connectors can result in significant savings in materials costs. For example, printed circuit board materials presently cost approximately $0.12 per square inch. This is a very high cost when one considers the volume of cards sold and the overall price of each card, and thus it would be very desirable to reduce the size of the card as much as possible. A reduction in width of one half inch for a typical eight inch interface card saves, at approximately $0.48 in material costs per card.
The second reason why placement of multiple connectors on a card without modification is lees than optimal is that the provision of three connectors on a card results in redundancies, previously unrecognized, which could be eliminated by sharing certain components between connectors, in particular housings, shielding, and the board locks used to mount the connectors on the card.